DOC: Minor changes to CONTRIBUTING

CONTRIBUTING.rst

@@ -11,22 +11,19 @@ newest development version from Github_::
 
    git clone https://github.com/spatialaudio/jackclient-python.git
    cd jackclient-python
-   python3 setup.py develop --user
-
-.. _Github: https://github.com/spatialaudio/jackclient-python/
+   python3 -m pip install --user -e .
 
+... where ``-e`` stands for ``--editable``.
 This way, your installation always stays up-to-date, even if you pull new
 changes from the Github repository.
 
-If you prefer, you can also replace the last command with::
-
-   python3 -m pip install --user -e .
+.. _Github: https://github.com/spatialaudio/jackclient-python/
 
-... where ``-e`` stands for ``--editable``.
+.. note::
 
-Whenever the file ``jack_build.py`` changes (either because you edited it or it
-was updated by pulling from Github or switching branches), you have to run the
-last command again.
+   Whenever the file ``jack_build.py`` changes (either because you edited it or
+   it was updated by pulling from Github or switching branches), you have to
+   run the last command again.
 
 If you make changes to the documentation, you can locally re-create the HTML
 pages using Sphinx_.